device-context

Arguments:
window

Returns an integer that identifies the device-context of
window if it has one, or nil otherwise. A device-context is a construct used
in the Windows API to specify a set of parameters that are used when
drawing on a window. A common graphics application does not normally
need to deal with a window's device-context directly, but if you need
to pass the window to a winapi function that calls for the window's
device-context (or hDC), then you should pass the integer returned by
this function for that argument. See also windows:handle, which
returns the window's "handle".

Every non-control window in common graphics (and every lisp-widget
window) is automatically assigned a device-context, which it keeps
until it is closed. Controls supplied by the OS (all controls except
lisp-widgets), on the other hand, are not automatically given
device-contexts in lisp since it is normally only the OS rather than
lisp that draws on the control. If you do want to draw directly on a
non-lisp control, then you must give the window of the control a
device-context while drawing on it. The easy way to do this is to wrap
a call to with-device-context around the code
that draws on the control.

Copyright (c) 1998-2012, Franz Inc. Oakland, CA., USA. All rights reserved.Documentation for Allegro CL version 9.0. This page was not revised from the 8.2 page.Created 2012.5.30.